And the secrets to how to use them effectively

My training philosophy
I pride myself on my dogs being well-trained and consequently well-behaved. It takes consistent work in the first few weeks and requires knowledge and patience, but the pay-off is a trouble-free relationship and a healthy, happy well-balanced dog who is sociable and responsive. It's far easier to put in some solid weeks of constant training at the start rather than spend your dog's lifetime dealing with behavioral problems. And key to this is basic training.
Control and sociability are the bedrock of a happy dog-human experience. For a dog to be calm, happy, healthy and well-balanced, they need to be able to exercise and play off leash; you can't give a dog the exercise they need while tethered to you, unless you're running, skating, scooting or cycling. And if they don't get the exercise they need, they will develop problem behaviors through frustration and restlessness.
Total Recall - 'I'll be back!'
So to go off-leash, in unenclosed areas, like the woodland we walk in every day, you need 100% recall so you can call your dog back at any moment. You also need a social dog who can play with others. All of this goes hand in hand. When a dog (or any animal) encounters another dog/animal, they will prepare to exhibit one of two responses - fight or flight. A dog on a leash knows it can't run away, so they can only prepare for fight, which means giving off a nervous or aggressive energy, which is not ideal for socializing.
In the UK, the law states your dog must be under control at all times. This means that if you don't have total recall, your dog is not under control when off the leash, or lead, as we say. So without recall, you can't walk them off the leash unless in an enclosed space, like a dog park.
So, my training regime is mainly focused on recall, initially, but the technique of positive affirmation - ignoring bad behavior and rewarding good behavior - is the same regardless of what you're working on. Below are my five training essentials and why I use them.

1. Training Books
Learn the basics before you do anything
New parents don't have their first child without gemming up on advice, be it from a book, a mother and baby class, a midwife or some other source of expertise. So why do so many new dog owners think they can bring an alien species into their home and not need to learn about its ways and needs? These days, there is no excuse with so many online sources of expertise, from blogs to training courses and YouTube videos.
Understanding how your dog thinks will transform your relationship and make training easier. So my bookshelf has basic training books, like The Dog Guardian by Nigel Reed and Cesar's Way by Cesar Millan (I learned a lot from Millan but later discovered the flaws of his dominance theory elements), but also deeper dives into the history and psychology of canines, like In Defence of Dogs by John Bradshaw, because understanding our amazing four-legged alien beast friends is deeply rewarding and will improve our interactions with every dog, forever. Even if every owner bought just one training book and only read chapter one, all dogs and owners would have a better life.
Click here to read my post on 'Our top five books about dogs'.
2. Treat Pouch and Treats
Positive training requires rewards
Dominance theory has driven canine training for decades and has been popularized by famous trainers such as Cesar Millan, The Dog Whisperer. Unfortunately, it is a flawed theory based on a study of captive wolves in the 40s, where Swiss animal behaviorist Rudolph Schenkel observed their use of dominance on each other, concluding the strongest wolf was the Alpha. This was unnatural behavior in a space too small for their needs, and they were not a 'pack' as they were drawn from many packs. Natural wolf behavior is much more egalitarian and closer to our own human family dynamic.
Today, it is accepted that positive affirmation is the way to train animals and using fear and exerting physical control over a dog can have serious negative consequences to their well-being. Be wary of any book or trainer that uses the terms 'alpha' or 'pack leader'.
And so to affirm the positive, you must reward. A reward can be affection, excitement, play and even just using their name in the appropriate, happy, tone. But nothing beats food treats. So while training, be sure to always have small titbit treats on you so you can reward any correct behavior, immediately (timing is absolutely key, but we'll come to that shortly).
You should reward with a treat every time your dog does what it is asked to do, but slowly over time replace the treat with affection, petting or their favorite toy. Then next time, go back to using food a few more times, then affection etc and no food, until eventually you have removed food treats and replaced with just positive affirmation in the form of verbal compliment or affection. But it's always a good idea to keep treats on you and reward intermittently with them, just to reinforce the training.
It's also a good idea to use different treats with different values of reward. For instance, if you're working on something new, or their attention is waning, use a higher value treat like some fresh chicken pieces, or cheese, or whatever they love. Then return to standard treats for everyday practice.
Cheesy trainer treats and a treat pouch
3. Long lead
Recall training is essential for safety
As soon as I got Rumble home from the rescue centre, training on the long lead began. I needed to learn about him before I could take him off leash. I didn't know if he was good with other dogs or if he was likely to bolt when he saw a squirrel. But I needed to exercise him too, so using a 20ft leash he was able to roam ahead and sniff out his new local environment and also play ball with me and interact with other dogs safely.
Check out my 'which is the best leash for you' post.
But the main use was to start recall training, using a whistle (and treats). And after just a couple of weeks, he was returning to me at every blast of the whistle. We then repeated everything off the leash in a secure enclosed space until I was confident of his recall. Within four weeks, we were practising walking to heel, off leash on the street - a short, quiet section (en route to the pub!), made longer each day, until he officially passed his training and was what I call 'free-range'.
4. Whistle
Let them roam but return every time
The whistle is my single most important item. It is always around my neck and is my remote control for Rumble. No matter where he is or what he's doing, he will always return with two blasts of the whistle. If he's in sight, and I want him to stop in his tracks, one blast makes him stop and sit down and wait for me, or for two blasts to return to me. (I always add a hand gesture, too, so that eventually I can do the same without the whistle, in stealth mode!)
Training recall on the whistle is relatively simple: I start by blowing the whistle at home, every time I put his dinner on the floor, literally the second it touches the floor. I also blow the whistle every time he gets rewarded with a treat, initially for simple commands like 'sit' and 'paw'. In no time the Pavlovian association between the sound and the reward of food is established.
Out in the park, I blow the whistle, he returns, and I blow it again just as the treat is given to him. You have a two or three second window between them doing what you've asked and rewarding them. Any longer and they might not associate the correct behavior with the reward.
And it's worth saying, in my opinion, it doesn't matter what kind of whistle you use. It doesn't have to be an ultrasonic type, audible only to your dog. I use a normal whistle like the example here. The most important thing is that you have it with you at all times.
5. Clicker
Teach them like a dolphin
And finally, what do you do if your dog correctly responds to a command, from a distance, but it takes longer than that two second window to come to you, or vice versa, to be rewarded? Too long and they won't make the connection.
This is where dolphin training comes in. When a dolphin performs his flip or trick, he's too far from the trainer to be instantly rewarded. The clicker was developed to affirm the correct action a trained dolphin performs just as he does it, and then clicked again when he swims to his trainer to be rewarded. So repeating the sound connects the action to the reward.
Clicker training is a very effective way of confirming correct behavior, but the timing is key and you mustn't click unless it's exactly the correct behavior - if they sit on command, but also bark as they do it, don't click, or you're affirming the barking, too. And when they sit, click the clicker as their butt touches the floor, and again as the reward touches their mouth.
Find this best-selling clicker here
So those are my basics, without going into too much detail. I also apply a hand gesture to all verbal commands so I can eventually control my dog silently. And I use two sounds - a negative ('Tssssst!') and a positive ('Clack!'), which mean different things in different contexts, such as 'Stop' and 'Go', or 'Leave' and 'As you were'. But that's for another time.
In the meantime, buy a book or two, or watch some YouTube videos, like Nigel Reed's Dog Guardian channel. And remember training is all about repetition and patience. Stay focused and don't give up. Good luck.